Agents acting on signalling molecules of growth pathways have emerged as therapeutic's for non-small cell lung cancer (NSCLC). Among them are inhibitors of the epidermal growth factor receptor (EGFR). To meet Belgian reimbursement criteria for erlotinib, patients must have an EGFR-positive tumour, defined as at least 10% of cells showing membranous staining on immunohistochemistry. This study compares results obtained with the Dako pharmDx kit versus other anti-EGFR antibodies in 634 NSCLC. More than 80% of patients qualify for erlotinib therapy using the Dako pharmDx kit or antibodies from Zymed or Novocastra; when NeoMarkers antibodies are used, less than 70% will do. Although immunohistochemical stainings for EGFR can be performed on biopsies, surgical and cytological samples from primary and metastatic NSCLC, highest positivity rates were obtained in biopsies from primary tumours. In conclusion, immunohistochemistry for patient selection for erlotinib therapy needs standardization in order to avoid results influenced by technical issues. (C) 2009 Elsevier Ireland Ltd. All rights reserved.